A virtual inspection framework for precision manufacturing of aerofoil components

The finite element method plays an extremely important role in forging process design as it provides a valid means to quantify forging errors and thereby govern die shape modification to improve the dimensional accuracy of the component. However, this dependency on process simulation could raise significant problems and present a major drawback if the finite element simulation results were inaccurate. This paper presents a novel approach to assess the dimensional accuracy and shape quality of aeroengine blades formed from finite element hot-forging simulation. The proposed virtual inspection system uses conventional algorithms adopted by modern coordinate measurement processes as well as the latest free-form surface evaluation techniques to provide a robust framework for virtual forging error assessment. Established techniques for the physical registration of real components have been adapted to localise virtual models in relation to a nominal Design Coordinate System. Blades are then automatically analysed using a series of intelligent routines to generate measurement data and compute dimensional errors. The results of a comparison study indicate that the virtual inspection results and actual coordinate measurement data are highly comparable, validating the approach as an effective and accurate means to quantify forging error in a virtual environment. Consequently, this provides adequate justification for the implementation of the virtual inspection system in the virtual process design, modelling and validation of forged aeroengine blades in industry.

FROM ASCRIPTION TO ACHIEVEMENT - ORIGINS, EDUCATION AND ENTRY TO THE LABOR-FORCE IN THE REPUBLIC OF IRELAND DURING THE 20TH-CENTURY

This paper examines the relationship between class of origin, educational attainment, and class of entry to the labour force, in three cohorts of men in the Republic of Ireland using data collected in 1987. The three cohorts comprise men born (i) before 1937; (ii) between 1937 and 1949; and (iii) between 1950 and 1962. The paper assesses the degree of change over the three cohorts in respect of (a) the gross relationship between origins and entry class; (b) the partial effect (controlling for education) of origin class on entry class; (c) the partial effect of education (controlling for origins) on class of entry. In broad terms the liberal theory of industrialism would imply a movement, over the three cohorts, towards (a) increasing social fluidity; (b) a weakening of the partial effect of origin class; (c) a strengthening of the partial effect of education. These latter two trends should be particularly noticeable in the youngest cohort, which would, to some degree, have benefited from the introduction of free post-primary education in Ireland in 1967.

Our results provide almost no support for these hypotheses. We find that patterns of social fluidity in the origin/entry relationship remain unchanged over the cohorts. The partial effect of class remains relatively constant; and, while the partial effect of education on entry class changes over the cohorts, the most striking result in this area is the declining returns to higher levels of education. While the average level of educational attainment increased over the three cohorts, the advantages accruing to the possession of higher levels of education simultaneously diminished. Taken together our results suggest that, in Ireland, those classes that have historically enjoyed advantages in access to more desirable entry positions in the labour market have been remarkably adept at retaining their advantages during the course of industrialization and through the various educational and other labour market changes that have accompanied this process.

After Slavery: Race, Labor and Citizenship in the Reconstruction South

an edited collection of essays exploring the variety of experiences of freedpeople in the post-emancipation United States. Co-edited by Brian Kelly and Bruce E. Baker, with an afterword by Eric Foner.

Fraternities and Labor Market Outcomes

We model how student choices to rush a fraternity, and fraternity admission choices, interact with signals firms receive about student productivities to determine labor-market outcomes. The fraternity and students value wages and fraternity socializing values. We provide sufficient conditions under which, in equilibrium, most members have intermediate abilities: weak students apply, but are rejected unless they have high socializing values, while most able students do not apply to avoid taint from association with weaker members.

Disinflation with labor market frictions

This paper studies disinflationary shocks in a non-linear New Keynesian model with search and matching frictions and moral hazard in the labor markets. Our focus is on understanding the wage formation process as well as welfare costs of disinflations in the presence of such labor market frictions.

The presence of imperfect information in labor markets imposes a lower bound on worker surplus that varies endogenously. Consequently equilibrium can take two forms depending on whether the no shirking condition is binding or not. We also evaluate both regimes from a welfare perspective when the economy is subject to a perfectly credible disinflationary shock.

Drive-by bridge inspection from three different approaches

This study presents a vibration-based health monitoring strategy for short span bridges utilizing an inspection vehicle. How to screen the health condition of short span bridges in terms of a drive-by bridge inspection is described. Feasibility of the drive-by bridge inspection is investigated through a scaled laboratory moving vehicle experiment. The feasibility of using an instrumented vehicle to detect the natural frequency and changes in structural damping of a model bridge was observed. Observations also demonstrated the possibility of diagnosis of bridges by comparing patterns of identified bridge dynamic parameters through periodical monitoring. It was confirmed that the moving vehicle method identifies the damage location and severity well.

A drive-by inspection system via vehicle moving force identification

This paper presents a novel method to carry out monitoring of transport infrastructure such as pavements and bridges through the analysis of vehicle accelerations. An algorithm is developed for the identification of dynamic vehicle-bridge interaction forces using the vehicle response. Moving force identification theory is applied to a vehicle model in order to identify these dynamic forces between the vehicle and the road and/or bridge. A coupled half-car vehicle-bridge interaction model is used in theoretical simulations to test the effectiveness of the approach in identifying the forces. The potential of the method to identify the global bending stiffness of the bridge and to predict the pavement roughness is presented. The method is tested for a range of bridge spans using theoretical simulations and the influences of road roughness and signal noise on the accuracy of the results are investigated.

Experimental investigation of a wavelet based drive-by bridge inspection system incorporating pattern recognition

This paper presents the results of an experimental investigation, carried out in order to verify the feasibility of a ‘drive-by’ approach which uses a vehicle instrumented with accelerometers to detect and locate damage in a bridge. In theoretical simulations, a simplified vehicle-bridge interaction model is used to investigate the effectiveness of the approach in detecting damage in a bridge from vehicle accelerations. For this purpose, the accelerations are processed using a continuous wavelet transform and damage indicators are evaluated and compared. Alternative statistical pattern recognition techniques are incorporated to allow for repeated vehicle passes. Parameters such as vehicle speed, damage level, location and road roughness are varied in simulations to investigate the effect. A scaled laboratory experiment is carried out to assess the effectiveness of the approach in a more realistic environment, considering a number of bridge damage scenarios.

After the Male Breadwinner Model? Childcare Services and the Division of Labor in European Countries

Fundamental reforms in childcare services appear to have eroded traditional
support to the male breadwinner model across European states. There has been a strong debate about the direction of these changes, and the ways in which childcare services can alter the division of labor and promote gender equality. This paper deals with these issues by using fuzzy set ideal-type analysis to assess the conformity of childcare service provisions in European economies to Fraser’s four ideal typical models: male breadwinner, caregiver parity, universal breadwinner, and universal caregiver. We find that there is resilience of traditional gender roles in the majority of European countries, while there are different variants of the universal breadwinner shaping different forms of childcare policies. The more equalitarian universal caregiver model maintains its utopian character.

An indirect bridge inspection method incorporating a wavelet-based damage indicator and pattern recognition

In recent years, there has been a move towards the development of indirect structural health monitoring (SHM)techniques for bridges; the low-cost vibration-based method presented in this paper is such an approach. It consists of the use of a moving vehicle fitted with accelerometers on its axles and incorporates wavelet analysis and statistical pattern recognition. The aim of the approach is to both detect and locate damage in bridges while reducing the need for direct instrumentation of the bridge. In theoretical simulations, a simplified vehicle-bridge interaction model is used to investigate the effectiveness of the approach in detecting damage in a bridge from vehicle accelerations. For this purpose, the accelerations are processed using a continuous wavelet transform as when the axle passes over a damaged section, any discontinuity in the signal would affect the wavelet coefficients. Based on these coefficients, a damage indicator is formulated which can distinguish between different damage levels. However, it is found to be difficult to quantify damage of varying levels when the vehicle’s transverse position is varied between bridge crossings. In a real bridge field experiment, damage was applied artificially to a steel truss bridge to test the effectiveness of the indirect approach in practice; for this purpose a two-axle van was driven across the bridge at constant speed. Both bridge and vehicle acceleration measurements were recorded. The dynamic properties of the test vehicle were identified initially via free vibration tests. It was found that the resulting damage indicators for the bridge and vehicle showed similar patterns, however, it was difficult to distinguish between different artificial damage scenarios.

Barriers to Subcontracted Labor Productivity in Urban Development Projects: An On-site Project Management Perspective

Considering the confined and complex nature of urban construction projects, labor productivity is one of the key factors attributing to project success. With the proliferation of sub-contracted labor, there is a necessity to consider the ramifications of this practice to the sector. This research aims to outline how project managers can optimise productivity levels of sub-contracted labor in urban construction projects, by addressing the barriers that most restrict these efficiency levels. A qualitative research approach is employed, incorporating semi-structured interviews based on three case studies from an urban context. The results are scrutinised using mind mapping software and accompanying analytical techniques. The findings from this research indicate that the effective on-site management of sub-contracted labor has a significant impact on the degree of success of an urban development project. The two core barriers to sub-contracted labor productivity are; 1) ineffective supervision of sub-contracted labor, and 2) lack of skilled sub-contracted labor. The implication of this research is that on-site project management play an integral role in the level of productivity achieved by sub-contracted labor in urban development projects. Therefore, on-site management situated in urban, confined construction sites, are encouraged to take heed of the findings herein and address the barriers documented. The value of this research is obtained through consideration of the critical factors; construction management professionals can mitigate such barriers, in order to optimise subcontracted labor productivity on-site.

Experimental investigation of drive-by bridge inspection

This study presents a vibration-based health monitoring of short span bridges by
an inspection vehicle. How to screen health condition of short span bridges in terms of the
drive-by bridge inspection is described. Feasibility of the drive-by bridge inspection is
investigated through a scaled laboratory moving vehicle experiment. The feasibility of using an
instrumented vehicle to detect the natural frequency and changes in structural damping of a
model bridge is observed. Observations also demonstrate possibility of diagnosis of bridges by
comparing patterns of identified dynamic parameters of bridges through a periodical
monitoring. It is confirmed that the method for damage identification under a moving vehicle
identifies the damage location and severity well.